Beta-D-glucan is a kind of polysaccharide which widely exists in bacteria, fungi, algae and plants, and one of the main sources of which is Saccharomyces cerevisiae. Yeast beta-D-glucan constitutes 30-60% by weight on a dry basis of yeast cell walls, and has a wide variety of physiological functions, such as enhancing immunity, anti-inflammation, antimicrobial, anti-infection, antiviral, anticancer, lowering cholesterol, anti-radiation and healing wounds. China is rich in yeast resources, and the fermentation industry, particularly the brewing industry can produce a large amount of waste Saccharomyces cerevisiae each year. In 2013, the beer yield is 50.615 million tons in total, with around 1 million tons of Saccharomyces cerevisiae being produced, but most of them are sold only as cheap feeds, or directly discharged into sewers as waste materials. This not only wastes resources, but also causes serious environment pollution. Thus, there is an urgent need for using the modern science and technology to enhance the comprehensive utilization of the waste Saccharomyces cerevisiae resources.
Methods for preparing S. cerevisiae beta-D-glucan mainly include acid method, alkaline method, enzyme method, ultrasonic method, and the like. There are a variety of preparation methods, but most of them are still limited in industrial scale production. Currently, the method widely used in the industrialized production of S. cerevisiae beta-glucan in China is alkaline method, by which the resulting product has high purity. However, the alkaline method would damage the structure of beta-D-glucan, and thus reduce its biological activity and restrict its use. Meanwhile, the alkaline solution would pollute the environment and damage the human health. The interactions of multi-hydroxyl groups in yeast beta-D-glucan molecules will form a compact triple helical structure, and thus making them insoluble in water, which restrict the application of yeast beta-D-glucan in the fields of food, medicine, cosmetics, etc. Therefore, it is very necessary to develop a green technology which is suitable for industrialization to prepare beta-D-glucan with high purity and high solubility under mild conditions.
Dynamic high pressure micro-fluidization (DHPM) technology, as a new means of food processing and handling, is integrated by many unit operations, such as transportation, mixing, superfine grinding, pressurization, heating, puffing, etc. Its working principle is achieving the modification of materials by high speed collision, high frequency oscillation, instantaneous pressure drop, cavitation effect, strong shearing action, etc. DHPM has gradually been widely used in preparation and modification process of polysaccharides.
There are many kinds of designable ionic liquids with unique properties, which can be applied in many fields. Ionic liquids mainly refer to the salts composed of organic cations and inorganic or organic anions, which are in liquid form at or near room temperature. As compared to the traditional organic solvents, ionic liquids have advantages of heat stability, extremely strong solubility, recyclability, and the like. As “green and designable” solvents, ionic liquids have drawn more and more attention in the fields of separation, dissolution, molecular assembly, and the like.
The Chinese patent application for invention with application number 201310003610.2 has disclosed a method for preparing yeast beta-D-glucan. However, the glucan produced by this method has very low solubility so as to be almost insoluble, which greatly limits its biological activity and also limits its practical application in industry.